Back in the day when every hotel that was charging for WiFi was stupidly leaving port 53 wide open, I wrote an IP over DNS tunnel to get free WiFi. Worked great until I went to a hotel in Tokyo and turned it on. Suddenly my network connection was completely dead. They were clearly watching for shenanigans. Took me a few minutes to figure out they had redirected my MAC address to the bit bucket. I spoofed my MAC to a different one, and then behaved, as well as admired those IT guys.